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Growth performance in Crossbred (Holstein x Gyr) dairy heifers differing in phenotypic residual feed intake

Paulo Campos Martins ; Mariana Magalhães Campos ; Juliana Aparecida Lima ; Fernanda Samarine Machado ; Luiz Gustavo Ribeiro Pereira ; Thierry Ribeiro Tomich ; Alexandre Lima Ferreira ; Sandra Gesteira Coelho
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The aims of this study were to quantify the variation in residual feed intake (RFI) of thirty-six heifers F1 (Holstein x Gyr) and evaluate their productive performance and body development. Thirty-six animals (146.7 ? 28.2 d of age and 152.3 ? 21.7 kg) were randomly housed in four paddocks, each one equipped with electronic feed bins (INTERGADO(R), Brazil) in Embrapa Dairy Cattle facilities (Coronel Pacheco, Brazil). Diet (75:25, corn silage:concentrate, 195 g CP/kg, DM basis) was fed ad libitum, twice a day, during 113 d of test. Feed intake was measured daily, body weight measured weekly. The morphometric measurements: withers height , hip height , rump width and chest circumference measures were carried out fortnightly using a flexible tape measure (Bovitec, SP, Brazil) and hipometer (Walmur, Porto Alegre, RS, Brazil). RFI was calculated for each animal as the difference between actual dry matter intake (DMI) and expected DMI. Expected DMI was computed for each animal by regressing average daily DMI (72 ? 10.9 d) on mean BW0.75and ADG over a 113 d period. Thirty-six animals were ranked according to the RFI into two groups: low (efficient) and high (inefficient). Regression analyses were conducted to estimate individual morphometric measurements on the middle of the efficiency test (205 d of age). The data were analyzed in a completely randomized design by ANOVA (P<0.06) using GLM procedure of SAS software. RFI of the low group (- 0.208 kg DM/d) was different of high group (+0.208 kg DM/d; P>0.05), equating to a difference of 0.416 kg of DM per day. There was no difference in ADG, DMI, rump width, chest circumference between RFI groups (P>0.05). Withers height (106.50 v. 104.38 cm) and hip height (112.06 v. 109.78 cm) were higher (P<0.06) for the low RFI group. There was no difference in majority morphometric measurements, except height between RFI groups. These results indicate an association between feed efficiency and animal height.